Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$187.61	6.806%	$200.3787	$200.38	$200.40	$200.40
Purchase #2	$165.83	5.365%	$174.7268	$174.73	$174.75	$174.70
Purchase #3	$211.33	13.808%	$240.5104	$240.51	$240.50	$240.50
Purchase #4	$162.60	4.285%	$169.5674	$169.57	$169.55	$169.60
Purchase #5	$113.40	8.820%	$123.4019	$123.40	$123.40	$123.40
Purchase #6	$26.84	13.620%	$30.4956	$30.50	$30.50	$30.50
Purchase #7	$131.37	6.109%	$139.3954	$139.40	$139.40	$139.40
7 purchase totals =	$998.98		$1,078.4762	$1,078.49	$1,078.50	$1,078.50